This invention relates to management of barring of incoming calls in a mobile telecommunications system.
FIG. 1 shows network elements and their mutual relations in connection with routing of a call in a known mobile telecommunications network PLMN (Public Land Mobile Network). The presented network is in accordance with the GSM system used as an example in this example. In this connection, a network means a mobile telecommunications network operated by one operator. The solid lines in the figure depict connections comprising both signalling and call connection whereas dashed lines depict such connections which comprise signalling only. The network includes base transceiver stations BTS able via a radio path to set up connections with mobile stations MS of mobile subscribers, base station controllers BSC controlling base transceiver stations and mobile services switching centres MSC. Under the MSC in the hierarchy there are typically several base station controllers BSC, while under these there are several base transceiver stations BTS. The call connections which have been set up pass from base transceiver station BTS via the base station controller BSC to the mobile services switching centre MSC, which connects calls either back to base station controllers under itself, to other mobile services switching centres MSC or to a fixed public switched telephone network PSTN or integrated services digital network ISDN. In addition, the network includes a network management system NMS which may be used for collecting information on the network state and for supplying information and programmes to other network elements.
It is characteristic of mobile telecommunications networks that the geographic location of mobile stations may change. For this reason, the network must maintain information on the locations of mobile subscribers. In the network of FIG. 1, this information is distributed to a home location register HLR and to visitor location registers VLR located in connection with mobile services switching centres MSC. The HLR, which is always in the subscriber""s own home network, contains unchanging subscriber information and information on the subscriber""s location with VLR precision. Information on the subscriber""s reachability and on the more precise location with so-called location area precision is stored in the VLR located in connection with the subscriber""s current mobile services switching centre VMSC.
FIG. 2 shows routing of a call. The figure names calling subscriber A""s home network PLMNA, called subscriber B""s home network HPLMNB and network VPLMNB visited by subscriber B. PLMNA, HPLMNB and VPLMNB may all be the same network operated by one operator (internal call of one operator) or networks operated by two or three different operators. The figure shows a case where subscriber A too is a mobile subscriber. If subscriber A is a fixed network subscriber, routing is exactly similar, but the GMSCA (Gateway MSCA) of subscriber A in the figure will be replaced with the GE (Gateway Exchange) of the fixed network.
FIG. 3 shows the signalling required when setting up a call. When setting up a call terminating in mobile station B, a connection is first set up with an initial address message IAM based on subscriber B""s subscriber number MSISDN(B) with the GMSCB (Gateway MSCB). The GMSCB asks for routing information from subscriber B""s home location register HLRB with SRI (Send_Routing_Info). Having received Send_Routing_Info, the HLRB performs a subscriber information check which is described more closely hereinafter. If no barrier to the incoming call is found in the subscriber information check, the HLRB will request the MSRN (Mobile Subscriber Roaming Number) from subscriber B""s present visitor location register VLRB with PRN (Provide_Roaming_Number). VLRB returns the MSRN number to HLRB in a PRN_ACK message. HLRB relays the MSRN to GMSC by a SRI_ACK message. GMSC sets up a connection with subscriber B""s MSCB using the identifying MSRN of called subscriber B.
Payments for calls are determined so that the calling subscriber, that is subscriber A, always pays for that part of the call which is between subscriber A and the home network of the called subscriber, that is subscriber B. The principle is that subscriber A, who does not know the location of subscriber B, will not have to pay any unpredictably high price for the call he makes. When outside his home network or when using a call forwarding service, subscriber B will pay for that part of the call which is forward from his home network. Hence when e.g. subscriber A is in Sweden and calls a New Zealand subscriber in Finland, subscriber A will pay for the part of the call from Sweden to New Zealand, while subscriber B will pay for the part going from New Zealand to Finland.
When far away from his own network, a subscriber may have to pay a considerable price for the calls he receives. For this reason, barring services for incoming calls are defined in GSM. Such services are e.g. BAIC (Barring of All Incoming Calls) and BIC-Roam (Barring of Incoming Calls when Roaming). Information about these barring services is stored in the subscriber""s home location register HLR.
The flow chart in FIG. 4 shows a subscriber information check of a call performed by the called subscriber""s home location register HLRB. Having received a SRI request (point 401), HLRB will search its database for the address of the called subscriber""s current visitor location register VLRB. At point 403 HLRB examines if the call is barred. If the call is not barred, progress will be made to point 404, where a PRN request is sent to VLRB, and the MSRN number received in response to the request is relayed to the exchange which made the routing information inquiry (point 406). If the subscriber has activated barring of incoming calls, HLRB will not send the Provide_Roaming_Number request of the signalling diagram in FIG. 3 to subscriber B""s visitor location register VLRB, but will send (point 411) an error message SRI_ERROR to the exhange which made the routing information inquiry SRI, stating barred call as the reason code.
In addition to checking of barring of incoming calls shown in FIG. 4, HLR also checks other matters, such as the existence of the called subscriber, any changes in the subscriber number, unconditional call forwarding to another number, and permission to the requested service. However, these are not essential from the viewpoint of the invention presented in this application, nor are they shown in the figure for this reason.
ETSI (European Telecommunications Standards Institute) is specifying a so-called optimal routing of calls for the GSM system, besides the normal call routing method presented above. The basic idea of optimal routing of calls is to use the straightest route possible between subscriber A and subscriber B as shown in FIG. 5. The home network of subscriber B does not necessarily take part in the call otherwise than as regards HLR signalling. By using optimal call routing, costs of calls between exchanges or centres can be saved and thus the total price of the call can be reduced.
The MoU (Memorandum of Understanding, the organisation of GSM operators) has imposed two requirements on the implementation of optimal routing:
1. use of optimal routing must not cause any price increase for any user, and
2. one subscriber always pays for one leg of the call at least in the first stage of the service.
Since it can not be assumed that the price of different legs of a call is known in the first stage of optimal routing, optimal routing is used in the first stage of the service only if GMSCA and VMSCB or VMSCB and HLRB are in the same country. The total cost of the call is hereby typically on the same level as a call made to the mobile station inside the same country.
Since optimal routing aims at routing the call using as direct a route as possible, it must be possible to make the HLR request at as early a stage as possible. If subscriber A is a mobile station in accordance with the same mobile telecommunications system as subscriber B, subscriber A""s GMSCA which supports optimal routing may make the inquiry. If subscriber A is not a mobile station in accordance with the same system as subscriber B, the call must be routed to such a network element which can make HLR inquiries, e.g. with the aid of pre-dialling agreed upon in advance.
The setting up of a call using optimal routing will be studied referring to FIG. 6, which shows the signalling used for call setup. GMSCA checks that subscriber B""s address belongs to a GSM subscriber, and if GMSCA supports optimal routing (OR1=Y), it sends a Send_Routing_Info request SRI(B,OR) for optimal routing to HLRB. HLRB receives the Send_Routing_Info request. If HLRB supports optimal routing (OR2=Y), it will check if at least one of the following conditions OR3 is fulfilled:
GMSCA is in the same country as VMSCB
HLRB is in the same country as VMSCB.
If at least one condition is met (condition OR3=Y) and no other barriers exist for setting up the call, HLRB will send a PRN request (Provide Roaming Number) to VLRB. From now on conditions OR3 will be changed in such a direction that a call can always be optimally routed, if the call using an optimised route is not more expensive either for subscriber A or for subscriber B than a normally routed call.
If VLRB supports optimal routing (OR4=Y), it will return the roaming number MSRN to HLRB in a PRN_ACK message. HLRB will send the roaming number MSRN to centre GMSCA, which will set up a direct connection with VMSCB with the aid of the MSRN number included in the IAM message.
If any one of conditions OR2, OR3 or OR4 is not fulfilled, HLRB will send an error message SRI_ERROR to GMSCA. If GMSCA receives the said error message or it does not itself support optimal routing (OR1=N), it will set up the call using a normal method as shown in FIG. 3.
The operation of HLRB in optimal routing as shown in FIG. 7 will now be studied. In addition to the checks shown in the figure, HLR also checks other matters, such as the existence of the called subscriber, any change in the number, unconditional call forwarding to another number, barring of all incoming calls (BAIC) and permission for the requested service. However, these are not essential from the viewpoint of the invention presented in this application, so they will not be presented in the figure.
Having received a routing information request SRI(B,OR) for optimal routing (point 702) HLR which supports optimal routing at point 704 searches its database for the address of subscriber B""s visitor location register. A check is made at point 705 of whether the call is barred, e.g. due to any activated BIC-Roam service. If the call is not barred, the above-mentioned condition OR3 for optimal routing will be checked. If OR3=Y, a PRN (Provide Roaming Number) request is sent to VLRB (point 707), and the roaming number MSRN obtained as a result of the request is returned to GMSCA at point 709.
If HLR does not support optimal routing (OR2=N), an error message SRI_ERROR is sent to GMSCA, in response to which GMSCA begins setting up a call using a normal method of call set-up, as shown in FIG. 3. If the call is barred, an error message SRI_ERROR is sent to GMSCA with xe2x80x9ccall barredxe2x80x9d as the reason code, in response to which GMSCA will release the call. If the condition OR3 for optimal routing is not fulfilled, a PSI inquiry (Provide_Subscriber_-Information) is sent to VMSCB, in response to which VMSCB will return information on the subscriber""s reachability state. If the subscriber is not reachable, call forwarding CFNRc (Call Forwarding on Not Reachable) defined in the not reachable state is examined, and if the subscriber is reachable, the error message SRI_ERROR is returned to GMSCA. In response to the error message SRI_ERROR, GMSCA will set up the call using normal routing.
If subscriber B MSB is outside his home network with the BIC-Roam service activated, set-up of the call is barred. It is a problem with the state of the art that this is done even if reception of the call would be considerably cheaper for subscriber B than the price of a normally routed call, in several cases even free, owing to optimal routing. However, a reduction of call charges of subscriber B is the basis for the entire BIC-Roam service, so barring of incoming cheap calls is not in accordance with the basic idea of the service. This invention aims at eliminating or at least at reducing this defect in the state of the art. This aim is reached with a method as defined in the independent claims.
The inventive idea is to define a set of permissible network elements based on location information of the called subscriber so that calls coming from these elements will be relayed to the called subscriber. Calls coming from outside this set will be barred. In connection with the invention the subscriber""s location information can be defined e.g.
as the country, where the subscriber did his latest location update,
as the network, to which the subscriber did his latest location update, or
as that network element VLR, to which the subscriber did his latest location update.
The set of allowed network elements may be defined e.g. as exchanges, the address of which fulfils a certain condition. Thus it may be determined that e.g. all calls coming from exchanges of the same country or the same operator shall be relayed to the called subscriber. It may also be determined e.g. that calls coming from certain countries or from the exchanges of certain operators shall be relayed.
The invention can be preferably applied together with BIC-Roam barring of incoming calls working outside the home network. With the method according to the invention barring of incoming calls can be bypassed, if reception of the call will cause only minor costs or no costs at all for subscriber B owing to optimal routing.
According to an advantageous embodiment, when the BIC-Roam service is activated only those optimally routed calls are relayed to the subscriber which come from the network where the subscriber is located at the time.
According to another advantageous embodiment, when the BIC-Roam service is activated only those optimally routed calls are relayed to the subscriber which come from the country where the subscriber is located at the time.
The function according to the invention is advantageously embodied in the called subscriber""s home location register, where a check according to the invention is added to the checking routines. The calling subscriber""s network element and the visitor location register VLRB to which the called subscriber has last done his location update are matters which are examined in the check. The incoming call will be relayed, if the network element of the calling subscriber belongs to the set of network elements determined on a location information basis and per called subscriber, from which incoming calls may be received by the said called subscriber by his own definition.
According to an advantageous embodiment of the invention, the information added to the subscriber""s location information which concerns network elements from which the subscriber is prepared to receive incoming calls, is divided into classes. Using a division into classes it is possible on a visitor register basis to determine several sets of networks elements, from which incoming calls will be relayed to their destinations. Hence the subscriber may easily determine a suitable class for himself by choosing to receive those calls, the reception of which will not be too expensive for him.